The Gates Foundation has been funding the study, prevention, and treatment of neglected infectious diseases for over a decade—since way before the current Ebola outbreak put neglected infectious diseases back on the global health funding map.

Having its finger on the pulse of such diseases, it’s not surprising that Gates has been funding dengue fever projects for over a decade, pouring over $150 million into this area. In recent years, though, dengue funding from Gates has fallen—at a time when outbreaks dubbed "unusual" are occurring around the world.

In Brazil, dengue fever has been an ongoing problem, but São Paulo is currently experiencing an outbreak of the mosquito-borne disease. By mid-February of this year, the city saw a 163 percent increase of the disease compared to the same time in 2014. Paradoxically, the city is also experiencing one of its worst droughts in history, so where are these disease-carrying bugs finding enough refuge to reach outbreak status?

For the most part, in makeshift water storage containers. As the São Paulo officials put it, they cannot govern how people store their water, especially when public water systems are rationed and city water is turned off for hours to days at a time. Brazil isn’t the only country seeing a spike in dengue:

Last fall, the WHO warned the world of a potential increase of dengue fever in Tokyo, which hasn’t seen the disease in its city since 1945

The island nation of Singapore also experienced a "sweeping epidemic" of dengue in 2013

Vietnam is currently experiencing an "unusual" dengue outbreak, with most of the fatalities being children.

Gates is arguably one of the foremost NGO funders of neglected infectious diseases like dengue, which is the main reason why it’s the focus of our attention here. But last year, Gates awarded just under $5.7 million in grants to dengue projects. The year prior, dengue funding topped out at around $62.5 million.

The most likely explanation of this 90 percent drop in funding is the Ebola outbreak. It isn’t unusual for a funder focused on neglected infectious diseases on such a broad spectrum as the Gates Foundation to shift its focus to more emergent diseases. In the case of Ebola, Gates hadn’t paid it any attention before 2014, when it doled out over $38.5 million toward battling the quickly spreading outbreak.

Now that Ebola is basically winding down (Liberia just released its last Ebola patient and hasn’t seen any new cases in the past week) and entering a recovery stage, perhaps Gates will shift its funding focus back to dengue, which seems to be just ramping up. It seems entirely possible given that out of the $5.7 million in dengue grants awarded last year, $4.8 million in grants were awarded at the end of the year. Meaning that dengue fever is definitely on the Gates Foundation’s mind.